The present invention relates to fabrication of semiconductor devices. More particularly, the present invention relates to chemicals for cleaning a deposition chamber.
Fabrication of semiconductor devices (integrated circuits or ICs) conventionally includes processing of substrates (wafers) in a number of chambers. In some of these chambers material is accumulated on chamber walls and the material must be periodically removed to avoid particle formation and to ensure stable chamber operation. The quantity of material deposited on chamber walls is particularly significant for deposition chambers such as chemical vapor deposition or physical vapor deposition chambers. It is preferable to clean such material without opening the chamber, i.e. by etching with a reactive gas to remove all the material in the form of a gas. Most types of material deposited on the walls in these chambers can be volatilized and then removed by exposing the walls to molecular or atomic fluorine.
The most direct source of fluorine atoms or molecules (F2) is F2 gas itself. However F2 is dangerous and difficult to handle. Thus it is preferred, in practice, to use compounds such as NF3 or SF6, or a mixture of CxFy (e.g., CF4, C3F8) and O2. To produce fluorine atoms or molecules, plasma is struck in the processing chamber itself or in a remote plasma source.
There are various disadvantages to using these gases for chamber cleaning purposes. For example, in the case of the CxFy/O2 mixture, the cleaning rate is low and the cleaning process produces large quantities of CO2. CO2 is a greenhouse gas that cannot be easily remediated and consequently is an environmentally undesirable by-product.
NF3 is expensive and difficult to obtain.
SF6 tends to cause sulfur contamination and accumulation in pump lines of chambers that it is used to clean.
As noted above, F2 is dangerous and difficult to handlexe2x80x94so much so that it is impractical to use as a chamber cleaning gas.
Accordingly it would be desirable to provide a more suitable substance as a cleaning gas precursor.
The present inventors have recognized that precursors that include iodine, including IF5 and IF7, are suitable for use in cleaning processing chambers. In accordance with the invention, a method of cleaning a processing chamber includes providing a processing chamber adapted to perform a process by which material accumulates on chamber components. The method further includes generating a reactive species from a precursor gas that includes iodine. Then to clean the chamber components they are exposed to the reactive species.
Although iodine-based precursors such as IF5 and IF7 are not free of disadvantages, they are believed to provide a more desirable balance of advantages and drawbacks than cleaning gas precursors that have conventionally been used. For example, IF5 is inexpensive, easy to obtain, and a good source of F atoms. Although IF5 is toxic, it is a liquid at room temperature and therefore easy to handle and store. However, because IF5 is liquid, the chamber cleaning system must include a suitable mechanism to generate a vapor from the IF5 for use as a cleaning gas.
IF7 is not as commercially available as IF5, but is a gas at room temperature and therefore can be used as a precursor without including a vapor generating mechanism in the cleaning system. IF7 can also easily be liquified to aid in handling and storage prior to use. Furthermore, one mole of IF7 contains seven moles of fluorine atoms. Thus more fluorine is produced from a mole of IF7 than from most other precursors. Though toxic, IF7 is an excellent source of F atoms and may prove to be price-competitive with conventional F precursor gases.
Accordingly, IF5 and IF7, when used as precursors in cleaning semiconductor processing chambers, may provide favorable trade-offs as compared to conventional cleaning gas precursors.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawing.